Japanese Patent Application No. 11-338146, filed Nov. 29. 1999, is hereby incorporated by reference in its entirety. Japanese Patent Application No. 2000-211079, filed Jul. 12, 2000, is hereby incorporated by reference in its entirety. International Application No. PCT/JP00/08384, filed Nov. 29, 2000 is hereby incorporated by reference in its entirety.
1. Field of Invention
The present invention relates to a RAM-incorporated driver that drives the display of still and moving images on one screen, together with a display unit and electronic equipment that uses the same.
2. Description of Related Art
Recent advances in communications and packaging technology have made it possible to display various types of highly informative data on a display section of a portable electronic equipment. The data can include not only character text consisting of numerals and characters, but also more complex data, such as still and moving images.
There have been various proposals for the format that should be used in displaying data by such electronic equipment. For example, in the case of a mobile telephone, a technique has been proposed for receiving or transmitting image data that has been compressed and encoded in accordance with the Moving Picture Experts Group (MPEG) standard. As shown, for example in FIG. 3, in such a case, received moving images are displayed on a moving-image display area 22A of a liquid crystal panel 22. Still images giving explanatory or operating information relating to those moving images are displayed on a still-image display area 22B of the liquid crystal panel 22, by way of example.
To display a moving image in the moving-image display area 22A, it is necessary to rewrite moving-image data in a moving-image storage area corresponding to the moving-image display area 22A, which is part of the storage area of a RAM within the liquid crystal driver. Of course, the moving-image data must be rewritten periodically and also substantially in real-time.
The still images displayed in the still-image display area 22B change in accordance with factors such as the operation of the keys of the mobile telephone, making it necessary to rewrite still-image data in a still-image storage area corresponding to the still-image display area 22B, within the storage area in a RAM. However, the rewriting of still-image data in the still-image storage area of the RAM periodically uses the bus line over which the moving-image data is being transferred, so it is only possible to use the gap between the transfer of one screen of moving-image data and the transfer of the next screen of moving-image data therefor.
In this manner, the transfer of still-image data within the limited times between screens of moving-image data can restrict the operating time in which the MPU can supply moving-image data and still-image data to the display unit, which increases the time-related restrictions on the operation of the microprocessor unit (MPU) for controlling circuits other than those of the display unit.
It is expected that future enlargements of the display area and increases in the number of gray scales will lead to moving images displayed on the display section that are even more complex, and which are easy to see and useful from the user's point of view. As the amount and complexity of the moving-image continues to increase, even more severe restrictions will be placed on the MPU's operating time. For that reason, it is preferable to enable transfer that moves moving-image data as rapidly as possible. On the other hand, it is also essential that a portable type of information terminal, such as a mobile telephone, which is convenient for displaying such informative information should have reduced energy consumption.